Fixing class casting exception for MachineLearningNodeClient GetMLTask API

[joshpalis]

Description

Following PR #1560, additional class casting issues have been observed for getMlTask

Issues Resolved

Coming from opensearch-project/flow-framework#131
Continuation of #1553 and #1580

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Merging #1616 (11e6c33) into main (06c0cc5) will increase coverage by 0.01%.
Report is 2 commits behind head on main.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #1616      +/-   ##
============================================
+ Coverage     79.43%   79.45%   +0.01%     
- Complexity     3982     3986       +4     
============================================
  Files           390      390              
  Lines         16215    16219       +4     
  Branches       1751     1751              
============================================
+ Hits          12881    12887       +6     
+ Misses         2660     2657       -3     
- Partials        674      675       +1     

Flag	Coverage Δ
ml-commons	79.45% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...pensearch/ml/client/MachineLearningNodeClient.java	98.41% <100.00%> (+0.05%)	⬆️

... and 2 files with indirect coverage changes

[opensearch-trigger-bot]

The backport to feature/agent_framework_dev failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-feature/agent_framework_dev feature/agent_framework_dev
# Navigate to the new working tree
cd .worktrees/backport-feature/agent_framework_dev
# Create a new branch
git switch --create backport/backport-1616-to-feature/agent_framework_dev
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 8f690fc84c0f93fec67a70b74ee01f3b1361033d
# Push it to GitHub
git push --set-upstream origin backport/backport-1616-to-feature/agent_framework_dev
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-feature/agent_framework_dev

Then, create a pull request where the base branch is feature/agent_framework_dev and the compare/head branch is backport/backport-1616-to-feature/agent_framework_dev.